The referenced resources are located in the game files. This resource contains references to all other resources that item has. Instead of cloning resources of potential interest, Harmony clones only the CAS Part.
This was true of all versions up to and including the Jackpot series. package with the assumption that they might be needed for editing. In the past, when Sims 4 Studio cloned a CAS item, many resources were added to the.
This post is intended to clear up some of the questions. There have been several questions related to the absence of resources in the Warehouse list when cloning a CAS item using Harmony.